There are two functions in Salesforce available only in the summary formula and considered the most powerful report formula. They are categorized under the Summary functions: PARENTGROUPVAL and PREVGROUPVAL.
Function formulas
The PARENTGROUPVAL() function
The PARENTGROUPVAL() function returns the value of a specified grouping; the grouping level is higher than the formula display level.
The formula syntax is different depending on the report format:
- In the Summary and Joined reports: PARENTGROUPVAL(summary_field, grouping_level)
- In the Matrix report: PARENTGROUPVAL(summary_field, parent_row_grouping, parent_column_grouping)